1. Field of the Invention
The field of the present invention is methods for filling and optionally emptying transport containers with plastics granular materials, emptying and filling systems therefore, as well as an inliner for use with transport containers to be filled or optionally emptied, and the use thereof.
2. Background
It is known to decant high-purity polycarbonate granular materials into big-bags to avoid contamination with foreign substances, or to empty the granular materials therefrom into other containers. Thus for example a bag-type collapsible container with an inliner, and also with filling and emptying hoses, is described in DE-A 35 39 619, which protects the transported material against contamination by impurities during decanting, transporting and emptying operations. The disadvantage of such big-bags is the relatively small capacity of ca. 800 to 1,000 kg and the unfavourable stacking volume and/or the resultant loss of load of ca. 4 tonnes of granular materials in 20 foot overseas containers, since instead of 20 tonnes in the case of a loose load, only ca. 16 tonnes can be accommodated in the form of stacked big-bags in a 20 foot container.
In the past there has been no lack of attempts to find suitable solutions to this problem of lost capacity in transport containers. Thus for example in WO-A 2000/41950 a silo vehicle is described for the bulk transportation of relatively large amounts of polycarbonate granular material, which enables the granular material to be handled while avoiding contamination with foreign substances. These silo vehicles are not economically feasible for use in overseas transportation and over long transport routes. In addition, this type of transportation has the disadvantage that the silo container can only be used in each case for the same goods, or that a complicated and expensive cleaning of the container is necessary if the material being transported is changed. This seriously complicates the procurement and deployment of the transporting means, especially for overseas traffic.
Accordingly there have already been suggestions to use inexpensive liners, known in specialist circles as so-called “inliners”, as replaceable protective sleeves in the interior of transport containers, which can have any desired shape and with the aid of which the above disadvantages can be overcome. This preference for the use of inliners in containers for transporting bulk goods has already been described in U.S. Pat. No. 3,696,952. There techniques are described for filling the inliner with bulk goods and for discharging the displaced air to the outside, and also emptying the inclined container via a chute inserted into the emptying opening. The filling procedure involves the use of pipes which are inserted into existing openings in the inliner, and are removed therefrom after the filling procedure; the remaining openings are sealed with thick paper for the transportation. Openings which are sealed in this way cannot guarantee the present stringent demands on hermeticity and reliably exclude contamination.
A method for emptying inliners in transport containers while avoiding damage to the inliner film is described in EP-A 627 368. In this, a transporting gas is blown under high pressure into the inliner of the horizontally arranged container, and at the outlet opening the bulk goods together with the transporting gas is discharged from the inliner through a pipe connection by applying a reduced pressure. Since the container does not have to be inclined, as is the case with discharge under gravity, the inliner cannot slip during the emptying procedure and is therefore also not damaged. The application of reduced pressure however runs the risk, even with only slightly non-hermetic pipeline connections, of drawing in air from the surroundings, and thus also runs the risk of contaminating high-purity granular materials with undesirable foreign particles. Accordingly, in a method employing reduced pressure extremely high demands are placed on the hermeticity of the pipelines that are used.
A method for emptying transporting means, for example railway wagons in enclosed facilities in order to avoid contaminating the flowable product to be decanted with impurities from the surroundings, is described in U.S. Pat. No. 5,639,188 and U.S. Pat. No. 5,868,528. The enclosed facilities that are used are in this connection sufficiently large so that the whole transporting arrangement (railway wagons, transporting containers) can be accommodated therein. By blowing in finely filtered, purified air by means of a circulation system no contamination with foreign substances or particles occurs when granular material comes into contact with the ambient atmosphere when the transporting device is opened. The conveyance of the material likewise takes place under reduced pressure and with purified air. The enclosed facilities required for this method are so large and the provision of filtered air is so costly, that the expenditure involved in a large number of discharge and decanting devices for granular materials is too high. Accordingly there is a need for a technically simpler but nevertheless reliable solution.
There was accordingly also a need for an economically advantageous and reliable method for decanting high-purity plastics granular materials, in particular polycarbonate granular material used for example for the manufacture of CDs, DVDs and other optical data carriers, while avoiding contamination by impurities in these decanting procedures, which can seriously affect the quality of the products. Since such contaminations can occur along the whole logistics chain, there was furthermore a need to provide such a method that is suitable for the filling procedure as well as the emptying procedure, and also for the employed transporting means. In this connection contact with contaminating foreign substances should in particular be avoided in all decanting procedures and during transportation. Since this technical solution also requires appropriate measures to be taken by the customer, it should be able to be carried out simply and reliably, and should be inexpensive. In addition an optimal space utilisation and the necessary provision and arrangement of overseas containers also have to be taken into account.
An object of the present invention is accordingly to provide such an economically advantageous and reliable method for granular material decanting procedures as well as the necessary technical systems and equipment for use in this method that do not have the disadvantages of the prior art.